In recent years, with increasing awareness of health issues, environmental issues and security issues, techniques for detecting trace amounts of biological substances and chemical substances relating to these issues have been demanded. As the techniques for detecting these objective substances to be detected, many techniques are suggested which measure the change of optical properties of a liquid specimen caused by the interaction of the specimen including the substances to be detected with a reagent or a sensor element. As for the methods for optically detecting these substances to be detected, many techniques of detecting the change of spectrum are proposed and/or developed as followings:
(1) a technique for detecting the change of an absorption spectrum caused by a reaction product produced through a chemical reaction including an enzyme reaction, or detecting the change of an absorbance for a particular wavelength; and
(2) a technique for detecting the change of the absorption spectrum or the absorbance for the particular wavelength by an agglomerate, through forming the agglomerate of fine particles through the substances to be detected, with the use of fine particles which immobilize a capturing body specifically coupled with the substances to be detected thereon.
These techniques acquire information by measuring spectrum with the use of a spectroscope, and accordingly have a problem of needing a period of time for scanning a necessary region of wavelengths. The problem can be improved by using a polychromator and an arrayed type detecting element, which eliminating the need for scanning the wavelengths. However, the device has constraint in the disposition of a light source, a sensing part for introducing a specimen and treating it for measurement, the polychromator and a detecting element for detecting the optical properties, and leaves the problem unsolved that the device is hardly miniaturized.
In addition, there is a sensor by using a surface plasmon resonance technique as is described in U.S. Pat. No. 6,183,696, as an example of solving the above described miniaturization problem by adopting a detecting technique without depending on the change of an absorption spectrum. The invention according to U.S. Pat. No. 6,183,696 has a characteristic in solving a problem of a mechanism for detecting a resonance angle, which has been a problem of the conventional surface plasmon resonance technique, by diffusive incident light and adopting a photodiode array. An advantage of this sensor is a point of simplifying a configuration of a detecting device, because of having a light-emitting element and a light-receiving element formed on the same plane. However, the device needs a length corresponding to a resonance angle in a contacting part with a specimen, or equivalently, needs a large size of a sensor surface for detecting one objective substance to be detected, and accordingly has a constraint for simultaneously detecting a plurality of the substances to be detected.
As a technique of solving the problem of a sensor area for detecting the above described one objective substance to be detected, among techniques using plasmon resonance, Japanese Patent No. 3452837 describes a sensor with the use of a localized plasmon resonance of metallic nanoparticles. A sensor element with the use of the localized plasmon resonance has an advantage of needing a very small area for a detecting element because of using metallic nanoparticles. However, the sensor element needs to detect a transmission spectrum or a reflection spectrum, and accordingly still leaves the same problem as in the above described technique of detecting the spectrum.
In addition, EP 1157266A1 discloses a sensor provided with a sensor chip having sensor chip units integrated crosswise and a phototransducer having the arrays of the phototransducer integrated crosswise, as a compact surface plasmon resonance sensor. FIG. 4 (a) shows a disclosed sensor having a light source and a detecting element array arranged on the same substrate, and a perception region of a sensor chip and a diffraction grating installed in an optical path between the light source and the detecting element array. The sensor disclosed here is persistently the surface plasmon sensor which reflects an emitted light from a light source by the sensor chip and introduces the reflected light to the detecting element array. In addition, the document does not describe a method of detecting a light which has been transmitted through the sensor chip and an application to the localized plasmon resonance.